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 A119258 Triangle read by rows: T(n,0) = T(n,n) = 1 and for 0
 1, 1, 1, 1, 3, 1, 1, 5, 7, 1, 1, 7, 17, 15, 1, 1, 9, 31, 49, 31, 1, 1, 11, 49, 111, 129, 63, 1, 1, 13, 71, 209, 351, 321, 127, 1, 1, 15, 97, 351, 769, 1023, 769, 255, 1, 1, 17, 127, 545, 1471, 2561, 2815, 1793, 511, 1, 1, 19, 161, 799, 2561, 5503, 7937, 7423, 4097, 1023, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS From Richard M. Green, Jul 26 2011: (Start) T(n,n-k) is the (k-1)-st Betti number of the subcomplex of the n-dimensional half cube obtained by deleting the interiors of all half-cube shaped faces of dimension at least k. T(n,n-k) is the (k-2)-nd Betti number of the complement of the k-equal real hyperplane arrangement in R^n. T(n,n-k) gives a lower bound for the complexity of the problem of determining, given n real numbers, whether some k of them are equal. T(n,n-k) is the number of nodes used by the Kronrod-Patterson-Smolyak cubature formula in numerical analysis. (End) LINKS Reinhard Zumkeller, Rows n=0..120 of triangle, flattened A. Björner and V. Welker, The homology of "k-equal" manifolds and related partition lattices, Adv. Math., 110 (1995), 277-313. R. M. Green, Homology representations arising from the half cube, Adv. Math., 222 (2009), 216-239. R. M. Green, Homology representations arising from the half cube, II, J. Combin. Theory Ser. A, 117 (2010), 1037-1048. R. M. Green, Homology representations arising from the half cube, II, arXiv:0812.1208 [math.RT], 2008. R. M. Green and Jacob T. Harper, Morse matchings on polytopes, arXiv preprint arXiv:1107.4993 [math.GT], 2011. OEIS Wiki, Sequence of the Day for November 3. K. Petras, On the Smolyak cubature error for analytic functions, Adv. Comput. Math., 12 (2000), 71-93. M. Shattuck and T. Waldhauser, Proofs of some binomial identities using the method of last squares, Fib. Q., 48 (2010), 290-297. M. Shattuck and T. Waldhauser, Proofs of some binomial identities using the method of last squares, arXiv:1107.1063 [math.CO], 2010. FORMULA T(2*n,n-1) = T(2*n-1,n) for n>0; central terms give A119259; row sums give A007051; T(n,0) = T(n,n) = 1; T(n,1) = A005408(n-1) for n>0; T(n,2) = A056220(n-1) for n>1; T(n,n-4) = A027608(n-4) for n>3; T(n,n-3) = A055580(n-3) for n>2; T(n,n-2) = A000337(n-1) for n>1; T(n,n-1) = A000225(n) for n>0.T(n,k)=[k<=n]*(-1)^k*sum{i=0..k, (-1)^i*C(k-n,k-i)*C(n,i)}; - Paul Barry, Sep 28 2007 T(n,k)=[k<=n] sum{i=n-k..n, (-1)^{n-k-i}*2^{n-i}*C(n,i)}. T(n,k)=[k<=n] sum_{i=n-k..n, C(n,i)*C(i-1,n-k-1)}. G.f. for T(n,n-k): x^k/(((1-2x)^k)*(1-x)). T(n,k) = R(n,k,2) where R(n, k, m) = (1-m)^(-n+k)-m^(k+1)*pochhammer(n-k,k+1)* hyper2F1([1,n+1], [k+2], m)/(k+1)!. - Peter Luschny, Jul 25 2014 From Peter Bala, Mar 05 2018 (Start): The n-th row polynomial R(n,x) equals the n-th degree Taylor polynomial of the function (1 + 2*x)^n/(1 + x) about 0. For example, for n = 4 we have (1 + 2*x)^4/(1 + x) = 1 + 7*x + 17*x^2 + 15*x^3 + x^4 + O(x^5). Row reverse of A112857. (End) EXAMPLE Triangle begins as:   1;   1, 1;   1, 3, 1;   1, 5, 7, 1;   1, 7, 17, 15, 1;   1, 9, 31, 49, 31, 1; MAPLE # Case m = 2 of the more general: A119258 := (n, k, m) -> (1-m)^(-n+k)-m^(k+1)*pochhammer(n-k, k+1) *hypergeom([1, n+1], [k+2], m)/(k+1)!; seq(seq(round(evalf(A119258(n, k, 2))), k=0..n), n=0..10); # Peter Luschny, Jul 25 2014 MATHEMATICA T[n_, k_] := Binomial[n, k] Hypergeometric2F1[-k, n-k, n-k+1, -1]; Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Sep 10 2017 *) PROG (Haskell) a119258 n k = a119258_tabl !! n !! k a119258_row n = a119258_tabl !! n a119258_list = concat a119258_tabl a119258_tabl = iterate (\row -> zipWith (+)    ( ++ init row ++ ) \$ zipWith (+) ( ++ row) (row ++ ))  -- Reinhard Zumkeller, Nov 15 2011 (PARI) T(n, k) = if(k==0 || k==n, 1, 2*T(n-1, k-1) + T(n-1, k) ); \\ G. C. Greubel, Nov 18 2019 (MAGMA) function T(n, k)   if k eq 0 or k eq n then return 1;   else return 2*T(n-1, k-1) + T(n-1, k);   end if;   return T; end function; [T(n, k): k in [0..n], n in [0..12]]; // G. C. Greubel, Nov 18 2019 (Sage) @CachedFunction def T(n, k):     if (k==0 or k==n): return 1     else: return 2*T(n-1, k-1) + T(n-1, k) [[T(n, k) for k in (0..n)] for n in (0..12)] # G. C. Greubel, Nov 18 2019 CROSSREFS Cf. A119259, A007318, A007051, A005408, A056220, A027608, A055580, A000337, A000225, A112857 (row reverse). A145661, A119258 and A118801 are all essentially the same (see the Shattuck and Waldhauser paper). - Tamas Waldhauser, Jul 25 2011 Sequence in context: A216948 A183944 A145661 * A099608 A247285 A047969 Adjacent sequences:  A119255 A119256 A119257 * A119259 A119260 A119261 KEYWORD nonn,tabl,easy AUTHOR Reinhard Zumkeller, May 11 2006 STATUS approved

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Last modified December 11 18:49 EST 2019. Contains 329925 sequences. (Running on oeis4.)